Segmental vertebral rotation in early scoliosis

Summary In order to investigate the development of the vertebral axial rotation in patients with early scoliosis, the vertebral rotation angle (VRA) was quantified on the basis of 132 anteroposterior radiographs obtained from patients with diagnosed or suspected scoliosis. The rotation was measured in the apical vertebra and in the two suprajacent and two subjacent vertebrae. The radiographic material was divided into a control reference group and three scoliotic groups with varying Cobb angle from 4° up to 30°. In the reference group a slight vertebral rotation was significantly more often seen to the right. In the scoliotic groups, the rotation was most pronounced in the apical segments. The mean VRA toward the convex side was significantly increased in the vertebrae just suprajacent to the apex in curves with a Cobb angle of 8°–15° and in the cranial four vetebrae in curves with a Cobb angle of 16°–30°. Atypical vertebral rotation to the opposite side of the major curve was observed in 12.8% of the cases. There was a significant positive correlation between the VRA and the Cobb angle. These results show that a slight VRA to the right is a common feature in the normal spine, and that the VRA increases with progressive lateral deviation of the spine. It is concluded that the coronal plane deformity in early idiopathic scoliosis is accompanied and probably coupled to vertebral rotation in the horizontal plane.     

Correction of flexible thoracic scoliosis below 65 degrees—A radiological comparison of anterior versus posterior segmental instrumentation applied to similar curves

Direct comparison of the correction of scoliosis achieved by different surgical methods is usually limited by the heterogeneity of the patients analyzed (their age, curve pattern, curve magnitude, etc.). The hypothesis is that an analysis of comparable scoliotic curves treated by different implant systems could detect subtle differences in outcome. The objective of this study was therefore: (1) to measure the 3D radiological parameters of scoliotic deformity and to quantify their postoperative changes, and (2) to compare the radiographic results achieved with one anterior and one posterior instrumentation methods applied to similar curves but representing different mechanisms of correction. Material and methods: The clinical notes and radiographs of 46 patients operated on for adolescent idiopathic scoliosis were reviewed. The inclusion criteria consisted of: a single thoracic curve, right convex, a frontal Cobb angle minimum of 45° and a maximum of 65°, flexibility on a lateral bending test of more than 30%, and a Risser test value of between 1 and 4. The operative procedures were: Cotrel-Dubousset instrumentation (CDI) for 25 patients (the CD group) and correction by anterior instrumentation (Pouliquen plate) for 21 patients (the ANT group). Preoperative and postoperative long cassette standing antero-posterior and lateral radiographs were examined. The frontal and sagittal thoracic Cobb angle, apical vertebra transposition (AVT), apical vertebra rotation (AVR), lowest instrumented vertebra (LIV) tilt, C7 vertebra shift and rib cage shift (RCS) were all compared. A computed reconstruction was produced with Rachis-91 software. Vertebral axial rotation angle was evaluated throughout the spine. Results: Postoperative assessment revealed a mean correction of the frontal Cobb angle of 37.0° for the CD group and 41.0° for the ANT group. The AVT operative correction was 45.8 and 42.7 mm, respectively, and AVR correction was 1.8 and 12.6°, respectively. The postoperative change of the sagittal Th4–Th12 Cobb angle was not significant for any method but it was significant (P=0.05) for the CD group if the curves were divided preoperatively into hypokyphotic and normokyphotic subgroups and then analyzed separately. Computed assessment demonstrated a correction of segmental axial rotation of more than 50% in the main thoracic curve in the ANT group, significantly more than that in the CD group (P<0.001). Conclusions: Anterior instrumentation provided better correction of the vertebral axial rotation and of the rib hump. CD instrumentation was more powerful in translation and more specifically addressed the sagittal plane: the postoperative thoracic kyphosis angle increased in the hypokyphotic curves and slightly decreased in the normokyphotic curves.     

Visualisation of the brace effect on the spinal profile in idiopathic scoliosis

We studied the brace effect on the spinal profile in idiopathic scoliosis, using a MR procedure visualising the complete scoliotic spine in any vertical plane, while rotating it 180° on the longitudinal axis of the patient. Thirty-eight female patients (mean age, 14.5 years) were included in the study. Inclusion criteria were an idiopathic scoliosis, a Cobb angle greater than 20°, age of 10–17 years and bracing with a Chêneau brace. The brace effect was studied in 38 thoracic curves. The MR examinations were carried out in direct sequences, with and without brace. A reconstruction algorithm allows visualising the whole spine in vertical projections, with rotational steps of 2°, from –90° to 90°, referred to as MR animation. In various vertical MR projections, the changes of the curves were evaluated by measuring the Cobb angle. Additionally, a translation angle of the apical vertebra was determined, representing the lateral deviation of the apical vertebra from a defined midline. Testing the reproducibility of the Cobb angles, the standard deviation of the intra-individual differences was 1.7° and of the inter-individual differences, 2.1°. For the translation angles, the standard deviation of the intra-individual differences was 0.8° and of the inter-individual differences, 0.9°. With brace the mean Cobb angle of the thoracic curves was significantly reduced in the various vertical MR projections. The mean translation angle was also reduced. MR analysis showed that the brace effect is a translation process, straightening the profile of the scoliotic spine in all vertical planes. MR animation allows visualising the brace effect on the spine in scoliosis based on a 3D data set, without additional radiation exposure. It showed the straightening effect of the brace leading to a flattening of the sagittal spinal profile.     

Inter- and intraobserver reliability assessment of the Cobb angle: manual versus digital measurement tools

The objective of this study is to determine the intraobserver and interobserver reliability of end vertebra definition and Cobb angle measurement using printed and digital radiographs of 48 patients with scoliosis. The Cobb angle and the end vertebra were assessed by six observers in 48 patients with scoliosis using printed and digital radiographs. Definition of end vertebra and measurement of the Cobb angle was repeated three times with a 3 week interval. Intraclass correlation coefficients (ICC) were used to determine the interobserver and intraobserver reliabilities. 95% prediction limits for the errors in measurements are provided. For the Cobb angle a mean ICC of 0.97 was determined for intra- and interobserver reliability measurement of the printed radiographs. For the electronic radiographs a mean ICC value of 0.93 was determined for interobserver reliability and a mean ICC value of 0.96 for intraobserver reliability. Intraobserver ICC for definition of end vertebrae was 0.8 for both methods. Interobserver ICC was 0.83 for the manual and 0.74 in the digital method. One pitfall in angle measurement implies the Cobb method itself which measures in two dimensions. Until we develop a proper tri-dimensional measuring system an error is introduced. For the Cobb angle measurement the definition of end vertebrae introduces the main source of error. Digital radiography does not improve the measurement accuracy.     

终板法与椎弓根法对青少年特发性胸椎脊柱侧凸Cobb角测量的比较

目的:对青少年特发性胸椎脊柱侧凸Cobb角测量的终板法和椎弓根法进行对比研究,比较两种方法的可信度、可重复性及两种方法测量结果的差异。方法:选取我院2010年7月～2011年3月门诊就诊的55例特发性胸椎脊柱侧凸患者,由一名高年资医师预先确定测量主弯的上、下端椎后,3名脊柱外科医师分别使用终板法和椎弓根法对站立位X线片进行手工测量评估,记录冠状面侧凸Cobb角数值,同时根据Nash-Moe法评估测量主弯上、下端椎的旋转度。1周后,打乱患者顺序,再由该3名医师重复测量。对测量结果进行可信度和可重复性分析,检验一致性并对两种方法的测量结果根据端椎旋转度和Cobb角大小分组进行分析比较。结果:终板法和椎弓根法测量主胸弯Cobb角的可信度和可重复性均为好～极佳的水平。终板法测量的总体可信度和可重复性分别为0.969和0.900,椎弓根法测量的总体可信度和可重复性分别为0.972和0.880。根据下端椎旋转度将AIS患者分组后的结果显示:下端椎无旋转组(Nash-Moe 0度)中椎弓根法与终板法测量结果无明显差异(P>0.05),而下端椎旋转明显组(Nash-MoeⅠ度和Ⅱ度)中椎弓根法测量结果较终板法小,差异有统计学意义(P<0.05)。根据Cobb角是否大于25°进行分组后的统计分析表明,在两组中椎弓根法测量结果均显著小于终板法(P<0.05)。结论:对于青少年特发性胸椎脊柱侧凸而言,终板法和椎弓根法测量Cobb角的可信度和可重复性均较好,但对于下端椎旋转明显(Nash-MoeⅠ度以上)的患者,椎弓根法较终板法测量结果小,建议对此类患者采用终板法测量Cobb角。     

Axial plane analysis of Lenke 1A adolescent idiopathic scoliosis as an aid to identify curve characteristics

Background context

Adolescent idiopathic scoliosis (AIS) is a complex three-dimensional (3D) deformity of the spine involving deviations in the frontal plane, modifications of the sagittal profile, and rotations in the transverse plane. Although Lenke classification system is based on 2D radiographs and includes sagittal thoracic and coronal lumbar modifiers, Lenke et al. suggested inclusion of axial thoracic and lumbar modifiers in the analysis.

Purpose

To analyze axial plane of Lenke 1A curves to identify curve characteristics.

Study design

Retrospective study.

Patient sample

Seventy patients (49 women, 21 men) with Lenke Type 1A idiopathic scoliosis were analyzed.

Outcome measures

Coronal, sagittal, and axial parameters were measured from plain radiographs that were obtained at initial medical examination of the patients.

Methods

Coronal and sagittal plane and whole spine segmental vertebra rotations from thoracic 1 to lumbar 5 were evaluated in 70 AIS patients with Lenke 1A curves by using Drerup method. Three different subgroups were identified according to magnitude and direction of lower end vertebra (LEV) rotation.

Results

In Group 1 (Lenke 1A1), the direction of LEV rotation was same with other vertebrae in the main curve and the magnitude of the LEV rotation was less than −0.5°. In Group 2 (Lenke 1A2), the rotation of LEV was between −0.5° and 0.5° and so was accepted as neutral. In Group 3 (Lenke 1A3), the rotation of LEV had opposite direction with vertebrae in the main curve and the magnitude of LEV rotation was more than 0.5°. The mean thoracic Cobb angle of patients with Lenke 1A idiopathic scoliosis was 51.1° (range 37°–80°), whereas the mean lumbar Cobb angle was 16.4° (range 0°–32°). The mean angle of trunk rotation of the patients was 5.7° (range 1°–16°). In terms of maximum thoracic vertebra rotation, the mean rotation angle of Lenke 1A idiopathic curves was −18.9° (range −(9.8°–44.7°)). The mean maximum lumbar vertebra rotation was 4.5° (range −7.2° to 15.1°).

Conclusions

Addition of axial plane analysis to conventional coronal and sagittal evaluations in patients with Lenke 1A curves may reveal inherent structural differences that are not apparent in single planar radiographic assessments and may necessitate a different surgical strategy.     

Disc and vertebral wedging in patients with progressive scoliosis

A retrospective longitudinal radiographic study of patients with progressive scoliosis was conducted to determine the relative amount of wedging between vertebrae and discs as a function of progression of the scoliosis curve, cause of the scoliosis, and anatomic curve region. Posteroanterior radiographs of 27 patients with idiopathic scoliosis and of 17 patients with scoliosis associated with cerebral palsy were studied. The amount of wedging of vertebrae and discs at the curve apex was measured by the Cobb method and expressed as a proportion of the curve's Cobb angle. On average, the relative amount of vertebral and disc wedging did not differ significantly between initial and follow-up radiographs made after progression of the scoliosis. In both groups of patients, the mean vertebral wedging was more than the disc wedging in the thoracic region; the converse was found in curves in the lumbar and thoracolumbar regions. The patients with scoliosis associated with cerebral palsy had curves that were longer and more commonly in the thoracolumbar and lumbar regions. The relative wedging did not change significantly with curve progression and did not appear to differ by diagnosis. In the management of scoliosis, including small curves, it should be recognized that both the vertebrae and discs have a wedging deformity.     

Threshold values for supine and standing Cobb angles and rib hump measurements: prognostic factors for scoliosis

Seven parameters recorded at the first clinical examination of 326 growing scoliotic patients were correlated with the speed of progression of the scoliotic curve during a natural history survey period. The parameters were: age; bone age (according to Greulich and Pyle); pubertal and Risser stage; curve shape; rib hump, measured in forward bending in a sitting patient and supine and standing radiographic Cobb angles of the scoliotic curve. The speed of progression of the scoliotic curve was expressed as the annual increase in Cobb angle. It was quantified graphically after plotting the measurements taken from all the radiographic examinations made during the survey. The survey period ranged from 6 months to several years, depending on the rate of progression. It was 6 months only if the scoliotic curve demonstrated worsening of more than 3° at two successive examinations performed at least 3 months apart. The authors aimed to identify the minimum values of curve angle and rib hump, identified at first examination in 95–100% of patients whose parameters at follow-up were above these values (supine angle: 17°; standing angle: 24°; rib hump: 11 mm), therefore demonstrating curve worsening. Then, they analysed how the other parameters such as age, bone age, state of maturation and curve shape influenced these threshold values of rib hump and supine and standing angles. The authors present the threshold values for the whole sample according to the sexual state of maturation and also for each curve shape. They demonstrate that a combination of states of maturation, several measures of the scoliotic curve and curve shape provides the best basis for individual prognosis.Paper read at the ESDS Meeting, 1994, Birmingham, and selected for full publication     

Reliability of assessing the coronal curvature of children with scoliosis by using ultrasound images

Purpose

To investigate the intra- and inter-observer reliability of the coronal curvature asymmetry of children with adolescent idiopathic scoliosis (AIS) using the center of lamina (COL) method on ultrasound (US) images.

Methods

A cadaver spinal column phantom which was manipulated to present 30 scoliotic curves of varying severity of scoliotic deformities was scanned using both the US and laser scanner (LS) systems. Three observers of varying experience and skill measured the coronal curvature using the Cobb method on the LS images and the COL method on the US images. All of the measurements were performed twice, with a 1-week interval to reduce memory bias. The intra-class correlation coefficient (ICC), the mean absolute differences (MAD), and the error index (EI) were calculated to determine the agreement on selecting the end vertebrae. In addition, five AIS subjects were scanned using the US system. One observer measured the coronal curvature on the US images twice, and the measurements were compared with the Cobb angle reported in the clinical records.

Results

In the phantom study, the COL method showed high intra- and inter-observer reliabilities, with all ICC values >0.88. The maximum MAD of the COL measurements between different sessions among all observers was <4.1°. The EI values of the US method had similar end-vertebra selections as the LS method. The results of the pilot study showed a high intra-reliability for the US measurements. The measured difference between the Cobb and COL methods was 0.7° ± 0.5°.

Conclusions

The COL method using US images appears to be a very reliable method for measuring the coronal curvature in AIS without the need to expose the patient to radiation.     

Volumetric determination of normal and scoliotic vertebral bodies

A new method is presented for stereological evaluation of the volume of the vertebral body in vivo. The height of the vertebral body is measured at three standardised points on an anteroposterior radiograph and at two other points on a lateral one. The area of the body is also measured using a special grid superimposed on a CT scan from the middle part of the vertebra. The volume of the vertebral body is then calculated using Cavalieri’s principle for irregular objects: V = Δa×H, where V is the volume of the vertebral body, Δa is the mean cross-section surface area on the CT scan and H is the mean of the heights at the five points on the radiographs, computed as mean weighted circumferential height. The volume of one normal and one scoliotic vertebra was evaluated in vitro using this formula. The obtained values were compared with the values derived from serial CT scans of the two vertebrae. The results showed that the volume of the normal vertebra measured with our new method was 15.9 cm³ and measured with serial CT scans using the same grid it was 15.07 cm³. For the scoliotic vertebra the values were 17.6 and 17.3 cm³, respectively. The degree of accuracy of the measurements with the presented method as compared with the serial CT method was 95% for the normal and 98.5% for the scoliotic vertebra. To prove the clinical applicability of the method, the heights of the apical and of the upper and the lower end vertebrae of the curve and the volume of the apical vertebrae were evaluted in eight scoliotic girls (nine curves) before and 3 years after spinal instrumentation and posterior fusion. The results showed that the mean circumferential height of the three vertebrae had increased significantly at the last follow-up. The volume of the apical vertebra had also increased, but the difference was not significant. It is concluded that the described method is easy to apply and has satisfactory accuracy for in vivo longitudinal studies of the volume of the vertebral body on radiographs and CT scans. Received: 27 September 1997 Revised: 3 February 1998 Accepted: 2 March 1998     

Structural vertebral changes in the horizontal plane in idiopathic scoliosis and the long-term corrective effect of spine instrumentation

Summary The rotation and structural changes of the apex vertebra in the horizontal plane as well as of the thoracic cage deformity were quantified by measurements on computed tomography (CT) scans from patients with right convex thoracic idiopathic scoliosis (IS). The CT scans were obtained from 12 patients with moderate scoliosis (mean Cobb angle 25.8°, r 13°–30°) and from 33 with severe scoliosis (mean Cobb angle 46.2°, r 35°–71°). In addition, CT scans of thoracic vertebrae from 15 patients without scoliosis were used as reference material. Ten of the scoliotic cases had had Cotrel-Dubousset instrumentation (CDI) and posterior fusion and had entered a longitudinal study on the effect of operative correction on the re-modelling of the apical vertebra. An increasingly asymmetrical vertebral body, transverse process angle, pedicle width and canal width were found in the groups with scoliosis as compared with the reference material. Vertebral rotation and rib hump index were significantly larger in patients with early and advanced scoliosis than in normal subjects. The modelling angle of the vertebral body, the transverse process angle index and the vertebral rotation in relation to the middle axis of the thoracic cage were significantly greater in patients with severe than with moderate scoliosis. The results of this longitudinal study suggest that the structural changes of the apical vertebra regress 2 years or more after CD instrumentation.     

Sagittal configuration of the spine and growth of the posterior elements in early scoliosis

The early changes of the sagittal alignment of the spine and the asymmetry between the posterior and anterior elements were determined on the basis of 134 lateral and 167 anteroposterior radiographs obtained from a control group and from patients with early scoliosis. The radiographs were allocated into four groups according to the degree of the Cobb angle. In thoracic curves with a Cobb angle of more than 8°, the kyphosis and the vertebral sagittal wedge angle decreased in comparison with the control group. The sagittal-wedge angle of the disc did not change significantly with increasing Cobb angle. The pedicle height in relation to the vertebral height, considered to represent the growth of the posterior element in relation to the growth of the anterior element, was not significantly different in the scoliotic groups as compared with the control group. The results indicate that changes of the sagittal configuration of the spine occur early in idiopathic scoliosis and that they are associated with disturbed growth of the vertebral body but not of the posterior elements. These findings seem to reflect a simulataneous deformation in the coronal and sagittal planes rather than a single growth disturbance in any specific plane.     

Is there a need for anterior release for 70–90° thoracic curves in adolescent scoliosis?

Large and stiff thoracic scoliotic curves in the adolescent represent a classic indication of anterior release followed by posterior instrumentation. However, third-generation segmental spinal instrumentations have shown increased correction of thoracic curves. Indication for an anterior release may therefore not be required even in large and stiff thoracic curves. The objective of the study was, therefore, to analyze retrospectively the results of third-generation segmental posterior instrumentation in large and stiff thoracic curves and to compare our results with the current literature of anterior release followed by posterior instrumentation. An independent observer, who had not participated in any of the case, reviewed our electronic database of adolescent scoliosis surgery (Scolisoft) with the following query: thoracic curves, Cobb angle between 70° and 90° and posterior surgery only. He was able to identify 19 patients whose thoracic curves were measured between 70° and 90°. Out of these, four had convex-side bending Cobb angle values of less than 45° and were not included in the study, as they were judged too flexible. Fifteen patients (aged 11–18 years, mean 13.6 years) with thoracic scoliosis were left for the study (average Cobb angles 78.5° with a flexibility index of 32.5% (range, 19–42%). The mean follow-up period was 32 months (range 18–64 months). Classic parameters of deformity correction were analysed. The average operative time was 314 min and the mean total blood loss was 1,875 ml. Average level of instrumented vertebrae was 12 (Range, 10–14). Postoperatively, the thoracic Cobb angle was measured at 34.8° (range, 25–45°), which represents a correction rate of 54% (range, 40.0–67.1%) and remained unchanged at the last follow-up (35°). Patients with thoracic hypokyphosis improved from an average 11° to 18°. There were three complications (one excessive bleeding, one early infection and one late infection). One case showed an add-on phenomenon at the last follow-up. Coronal balance was improved from 1.8 cm (Range 0–4cm) down to 0.75 cm (range 0–2.5 cm). Shoulder balance was improved from 1.3 cm (range 0–4cm) down to 0.75 (0–2.5 cm). All patients reported satisfactory results except the patient with an adding-on phenomena. In the literature, most of the results of anterior thoracoscopic release and posterior surgery give a percentage of Cobb angle correction similar or inferior to our series for an average initial Cobb angle of less magnitude. Therefore, with adequate posterior release, and the use of third-generation segmental instrumentation there is no need for anterior release even for curves in the 70 –90° range.     

Evaluation of deformities and pulmonary function in adolescent idiopathic right thoracic scoliosis

Summary Seventy patients with adolescent idiopathic right thoracic scoliosis had full assessment of their pulmonary function using a computerised pulmonary function system. Their mean age at evaluation was 13.8 years. The following measurements were obtained from anteroposterior and lateral standing and antero-posterior supine bending radiographs: lateral curvature, vertebral rotation, kyphosis, maximum sterno-vertebral distance and apical rib-vertebral angles. Using the above measurements, the flexibility of curve, vertebral rotation and rib-vertebral angle asymmetry were calculated. Patients were classified into three groups on the basis of their predicted vital capacity, to determine whether radiological features of deformity can help identify patients with compromised pulmonary function. The mean Cobb angle and vertebral rotation for the 70 patients were 50° (range 35–100°) and 22° (range 1–44°) respectively. The mean flexibility of curve and vertebral rotation were 52% and 49% respectively. Mean thoracic kyphosis was 25%, ranging from -7 to 55%. Of the patients with Cobb angle less than 90%, 71% had vital capacity less than 80% of predicted values, and of these, 18% had marked compromise of vital capacity (less than 60% of predicted values). Mean values of Cobb angle, vertebral rotational flexibility, kyphosis, rib-vertebral angle asymmetry (in standing as well as supine bending radiographs) differed significantly between patients with more than 80% of predicted vital capacity and those with 60% or less of predicted values. Radiological features indicative of better pulmonary function were: rotational flexibility exceeding 55%, rib-vertebral angle asymmetry (standing) less than 25% and kyphosis greater than 15%. Two deformity parameters—that give a better prediction of pulmonary function than the widely used Cobb angle, vertebral rotational flexibility and rib-vertebral angle asymmetry—were identified in this study.     

A comparative study of computed tomographic and plain radiographic methods to measure vertebral rotation in adolescent idiopathic scoliosis.

A comparative analysis of two methods of measuring vertebral rotation in adolescent idiopathic scoliosis is reported in this article. Nash and Moe's pedicle shift method (using plain anteroposterior radiographs) is compared with a new method using computed tomographic scans. The computed tomographic scans of the whole length of the major curve and the scout films obtained from seventeen girls aged 12.5-14 years were measured for rotation of each vertebra of the curve (total number of vertebrae measured by two methods = 173). This study has three interesting new findings: 1) Those vertebrae with Nash & Moe grade 0 had up to 11 degrees of vertebral rotation when measured using the computed tomographic method. Therefore, Nash & Moe's grade '0' is not a neutrally rotated vertebra; 2) For Nash & Moe grade 1 and 2, the computed tomographic method revealed statistically significantly greater rotation for lumbar vertebrae than thoracic vertebrae. There was a similar pattern for Nash & Moe grade 0 but these differences were not statistically significant; and 3) Simple formulae are reported to convert Nash & Moe's grades into angle of vertebral rotation as obtained by CT method separately for thoracic and lumbar vertebrae.     

Time series spinal radiographs as prognostic factors for scoliosis and progression of spinal deformities

The effectiveness of clinical measures to predict scoliotic progression is unclear. The objective of this study was to identify potential prognostic factors affecting scoliosis progression. Consecutive measurements (181) from 35 non-instrumented adolescent idiopathic scoliosis patients with at least two follow-up assessments were studied. Potential prognostic factors of gender, curve pattern, age, curve magnitude, apex location and lateral deviation and spinal growth were analyzed. Stable and progressed groups were compared (threshold: Cobb angle ≥5° or 10°) with sequential clinical data collected in 6-month intervals. Double curves progressed simultaneously or alternatively on curve regions. Age was not significantly different prior to and at maximal Cobb angle. Maximal Cobb angles were significantly correlated to initial Cobb angles (r = 0.81–0.98). Progressed males had larger initial Cobb angles than progressed females. Apex locations were higher in progressed than stable groups, and at least a half vertebra level higher in females than males. Maximal apex lateral deviations correlated significantly with the initial ones (r = 0.73–0.97) and moderately with maximal Cobb angles (r = 0.33–0.85). In the progressed groups, males had larger apex lateral deviations than females. Spinal growth did not relate to curve progression (r = −0.64 to +0.59) and was not significantly different between groups and genders. Scoliosis may dynamically progress between major and minor curves. Gender, curve magnitude, apex location and lateral deviation have stronger effects on scoliosis progression than age or spinal growth. Females with high apex locations may be expected to progress.     

Rib-vertebral angle asymmetry in idiopathic, neuromuscular and experimentally induced scoliosis

The concave and convex rib-vertebral angle (RVA) at levels T2–T12 was measured on AP radiographs of 19 patients with right convex idiopathic thoracic scoliosis and 10 patients with major thoracic right convex neuromuscular scoliosis. The difference between the angles on the concave and the convex sides, the RVAD, was calculated. The RVAs were also measured on radiographs from three animal groups in which spinal curves had been induced experimentally in a variety of ways. Group 1 comprised 16 rabbits that had been subjected to selective electrostimulation of the latissimus dorsi, the erector spinae and the intercostal muscles. Group 2 comprised four dead rabbits whose spines had been subjected to manual bending. Group 3 comprised eight rabbits that had undergone mechanical elongation of one rib. In both the idiopathic and the neuromuscular group, the convex RVA was smaller than the concave RVA between levels T2 and T8, with a maximal difference between T4 to T5. From T9 to T12 the concave RVA was smaller than the convex. The RVA in relation to the scoliotic segment, i.e. the apex level of the curve and the two neighbouring vertebrae above and below this level, showed similar results. With increasing Cobb angle the RVADs increased linearly with the greatest difference at the second vertebra above the apex. In the three experimental groups the pattern of the RVADs between T6 to T12 was basically similar to the findings of the clinical study. From the results of these clinical and experimental studies, it is concluded that the typical pattern of the RVAs on the concave and convex sides seems to be independent of the underlying cause of the spinal curvature. It is likely that the RVADs result from a passive mechanical adaptation of the ribs to the lateral curvature of the spine.     

Measurement of vertebral rotation: Perdriolle versus Raimondi

Summary The measurement of vertebral rotation according to Perdriolle is widely used in the French-speaking and Anglo-American countries. Even in this measurement technique there may be a relatively high estimation error because of the not very accurate grading in steps of 5°. The measurement according to Raimondi seems to be easier to use and is more accurate, with 2° steps. The purpose of our study was to determine the technical error of both measuring methods. The apex vertebra of 40 curves on 20 anteroposterior (AP) radiographs were measured by using the Perdriolle torsion meter and the Regolo Raimondi. Interrater and intrarater reliability were computed. The thoracic Cobb angle was 43°, the lumbar Cobb angle 36°. The average rotation according to Perdriolle was 19.1° thoracic (SD 11.14), 12.7° lumbar (11.21). Measurement of vertebral rotation according to Raimondi showed an average rotation of 20.25° in the thoracic region (11.40) and 13.4° lumbar (10.92). The intrarater reliability was r=0.991 (Perdriolle) and r=0.997 (Raimondi). The average intrarater error was 1.025° in the Perdriolle measurement and 0.4° in the Raimondi measurement. Interrater error was on average 3.112° for the Perdriolle measurement and 3.630° for the Raimondi measurement. This shows that both methods are useful tools for the follow-up of vertebral rotation as projected on standard X-rays for the experienced clinicial. The Raimondi ruler is easier to use and is slightly more reliable.     

Reliability assessment of Cobb angle measurements using manual and digital methods

Background contextThe vertebral spine angle in the frontal plane is an important parameter in the assessment of scoliosis and may be obtained from panoramic X-ray images. Technological advances have allowed for an increased use of digital X-ray images in clinical practice.PurposeIn this context, the objective of this study is to assess the reliability of computer-assisted Cobb angle measurements taken from digital X-ray images.Study design/settingClinical investigation quantifying scoliotic deformity with Cobb method to evaluate the intra- and interobserver variability using manual and digital techniques.Patient sampleForty-nine patients diagnosed with idiopathic scoliosis were chosen based on convenience, without predilection for gender, age, type, location, or magnitude of the curvature.Outcome measuresImages were examined to evaluate Cobb angle variability, end plate selection, as well as intra- and interobserver errors.MethodsSpecific software was developed to digitally reproduce the Cobb method and calculate semiautomatically the degree of scoliotic deformity. During the study, three observers estimated the Cobb angle using both the digital and the traditional manual methods.ResultsThe results showed that Cobb angle measurements may be reproduced in the computer as reliably as with the traditional manual method, in similar conditions to those found in clinical practice.ConclusionsThe computer-assisted method (digital method) is clinically advantageous and appropriate to assess the scoliotic curvature in the frontal plane using Cobb method.     

Measurement of vertebral rotation in idiopathic scoliosis using the Perdriolle torsionmeter: a clinical study on intraobserver and interobserver error

Summary This study was designed to determine the reliability and accuracy of the Perdriolle torsionmeter. Fifty-four observers were divided into three groups according to their previous experience in the field of orthopaedics and the treatment of scoliosis. Each observer, on two separate occasions, measured the apical vertebral rotation on preoperative and postoperative roentgenograms of three idiopathic thoracic scoliotic curves using the torsionmeter. For all groups, there was no statistically significant difference (P>0.05) between the average of the first and the average of the second measurements of vertebral rotation of any of the curves. In the curve with the highest frontal Cobb angle and vertebral rotation of more than 30°, there was a statistically significant difference (P=0.03) between the average measurements of the three groups of observers. We concluded that, as both intraobserver and interobserver error risks were insignificant, the torsionmeter can be accurately used by everyone in the fields of orthopaedics provided the vertebral rotation is not greater than 30° and the curve is mild or moderate. The reliability and accuracy of the torsionmeter was found to be questionable at more than 30° of vertebral rotation because of increased risk of interobserver error.This study was presented as a free paper at the SICOT Regional and 14th National Turkish Congress of Orthopaedic Surgery and Traumatology, 29 September–4 October 1995, Izmir